Systems and methods of three-dimensional printing of collimators using additive approaches

ABSTRACT

A method of manufacturing a collimator ( 134 ) on a three-dimensional printer ( 510 ) includes obtaining design specifications ( 536 ) for the collimator, the design specifications including a channel perimeter pattern and an overall collimator thickness, determining a first quantity of deposit layer permutation types based on the channel perimeter pattern, determining a respective second quantity of permutation layer elements ( 310, 320, 330 ) for each respective one of the deposit layer permutations, generating respective sets of sequences for each respective one of the deposit layer permutations, the number of sets equal to the respective second quantity for the corresponding deposit layer permutations, assembling the respective sets of sequences into a three-dimensional print file ( 538 ), providing the three-dimensional file to the three-dimensional printer, and manufacturing the collimator by depositing additive layers of material based on contents of the three-dimensional file. A system for implementing the method and a non-transitory computer-readable medium are also disclosed.

BACKGROUND

Single Photon Emission Computed Tomography (SPECT) imaging systemsinclude a collimator in the path of radioisotope emitted by anobject-under-study and a detector (e.g., a photomultiplier tube, or thelike). The choice of collimator design can have an impact on thesensitivity and resolution of the SPECT system.

The collimator acts as the front-end of a gamma camera, and has a bigimpact on the signal-to-noise ration of the captured image. Thecollimator functions to spatially control the propagation direction(i.e., field-of-view) of the gamma rays reaching the detector—similar toa lens used in visible photon wavelengths. SPECT collimators aretypically formed from radiation-absorbent material, where non-absorbedphotons can reach the detector.

FIG. 1 is a diagram of conventional SPECT scanner imaging system 100.SPECT scanner system 100 includes gantry 120 to which two or more gammacameras 130 a, 130 b are attached, although other numbers of gammacameras can be used. Detector 132 in the gamma ray camera detects gammaphotons 140 emitted by a radioisotope within the body of a patient 145lying on a bed 150. Collimator 134 is positioned between the emittedphoton and the detector. Bed 150 is slidable along axis-of-motion A. Atrespective bed positions (i.e., imaging positions), a portion of thebody of patient 145 is positioned between gamma cameras 130 a, 130 b andan image of that body portion is captured.

Control processor 110 can execute instructions to control operation ofthe SPECT scanning system. Motion control/automation module 112 cancontrol motors, servos, and encoders to cause gamma cameras 130 a, 130 bto rotate along gantry 120, and to move bed 150 along an axis-of-motion(arrow A). Data acquisition/image processing module 114 can acquireprojection data at defined imaging position points during the rotationof gamma cameras 130 a, 130 b and/or the shifting of bed 150. Theacquired data can be stored in memory 118. Imaging processing algorithmscan manipulate the stored projection data to reconstruct a 3D image. Thereconstructed 3D image can be displayed on an interactive displaycontrolled by operator interface/display module 116.

Conventional attempts to use commercially-available, off-the-shelfthree-dimensional (“3D”) printers to produce the collimator patternscommonly used in SPECT have not achieved satisfactory results.Conventional 3D printing of collimators fails to meet the qualityrequired for medical imaging (e.g., tolerances, uniformity,manufacturability, etc.).

There are significant challenges in making use ofcommercially-available, additive processes to produce medical-modalitycollimators on a 3D printer. One reason is that the required tolerancescannot be guaranteed using 3D printers' additive processes due to thehigh viscosity of the extruded filament print material, which is madeeven higher when imbedded with high-density and high-atomic number (“Z”)materials (required to increase the attenuation of ionizing radiation).Limitations controlling the position and speed of the extrudingprinthead relative to the flow of the extruded material also contributeto the challenges. Because of these factors, the conventional approachof producing stereolithography files (e.g., STL format) directly from 3DCAD files is not a viable solution. Further, conventional approaches tomanufacturing collimators by 3D printing fail to yield devices that meetquality requirements of medical imaging (tolerances, uniformity,manufacturability, etc.) using off-the-shelf components.

In recent years, vendors of 3D printed collimators have been proposinggreen manufacturing processes (e.g., Pb-free and RoHS-compliant) thatrequire special printing processes which require significant investmentand add cost to the end products. None of these processes have beensuccessfully produced in scale to replace current available leadcollimators. The cost for these conventional 3D printed collimators isgreater than existing lead collimators.

There is a need in the art to quickly, and accurately createmedical-modality collimators by applying layered 3D printing techniquesusing information contained in a stereolithography file.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a conventional SPECT scanner imaging system;

FIG. 2A depicts a conventional 3D printer trajectory path;

FIG. 2B depicts a predicted resulting cumulative deposit for thetrajectory path of FIG. 2A;

FIG. 2C depicts a synthesized cumulative result for the trajectory pathof FIG. 2A;

FIG. 3A depicts multiple layers of a 3D printer trajectory path, and itspredicted cumulative deposit in accordance with embodiments;

FIG. 3B depicts synthesized results for individual layers and asynthesized cumulative result for the multiple layers depicted in FIG.3A in accordance with embodiments;

FIG. 4 depicts a process to create a 3D print file in accordance withsome embodiments; and

FIG. 5 depicts a 3D printer system for producing a collimator inaccordance with embodiments.

DETAILED DESCRIPTION

Embodying systems and methods implement one or more layered-permutationsequence algorithms that specify the content of a stereolithography(“STL”) file used to instruct a 3D printer to produce a collimator usingan additive, layered process. The printed collimator is extruded layerby layer using 3D printer filament, to form a collimator of suitablethickness for its intended medical modality. Systems and methods specifyeach layer representation within the STL file in a predetermined orderto achieve a collimator capable of operating within required performancespecifications.

A collimator manufactured by these techniques can be applicable forvarious medical modalities (e.g., SPECT, CT, and others). For purposesof this disclosure, a SPECT system collimator will be discussed.However, the invention is not so limited, it should be readilyunderstood that other medical-modality collimators are within the scopeof this disclosure.

In accordance with embodiments, a 3D printed collimator with requiredtolerances and overall quality, and having a large field-of-view can beproduced using off-the-shelf components from an STL file created byembodying algorithms. Embodying system and methods can have directapplications in fast-prototyping operable collimators for test/prove-outof new designs. Embodying approaches distinguish over conventionaltechniques by being able to quickly print and test new collimatordesigns (for performance compatibility/impact with improved imagereconstruction algorithms).

This distinction over the prior art can be of great value to improvingcurrent and future SPECT systems and applications. Embodying systems andmethods make possible the manufacture of medium-energy SPECT collimatorsusing commercially available 3D printing off-the-shelf components.

FIG. 2A depicts conventional 3D printer trajectory path 200, whichillustrates the segments covered by the printhead. The printhead beginsa forward trajectory at position 0 and ends its travel at position 115;retraces itself in a reverse trajectory from position 115 to position 0;and repeats forward and reverse trajectories until the layered materialis at a specified height.

FIG. 2B depicts predicted 3D printed pattern. This predicted pattern canbe an idealized version from the contents of the CAD drawing used tocreate the conventional STL file. FIG. 2C depicts an illustration ofactual 3D printed pattern, which is the result of the conventionalapproach to 3D printing of the collimator.

As illustrated by the examples of FIGS. 2A-2C, under conventionaltechniques, the required size and tolerances of collimators aredifficult (perhaps impossible) to maintain using the conventionaldirect-conversion of CAD files into STL files while using traditional 3Dprinting methods (forward trajectory, reverse trajectory, and repeatcycle) with off-the-shelf components.

Drawbacks in the conventional approaches result from, for example, the3D printhead is required to re-trace itself along the same path duringthe additive process detailed in the conventional STL file; and/ormaneuvering through sharp turns (e.g., about 60° or greater) during itstrajectory. These features are not properly achieved when created by a3D printer extruding conventional materials per information provided bya conventional STL file.

FIG. 3A depicts multiple layers 310, 320, 330 of a 3D printer trajectorypath, and predicted cumulative deposit 340 in accordance withembodiments. Each of multiple layers 310, 320, 330 represents arespective trajectory path for the printhead, where each layer describesa respective path along which the printhead does not retrace itself toproduce that respective individual layer. For this example, whenoverlapped the multiple layers form a triangular lattice.

Layer 310 depicts a printhead path with two connected sets of aboutparallel lines, where one set of lines is orthogonal to the other. Theprinthead moves along the trajectory path. Layer 320 depicts a printheadpath with one set of lines rotated clockwise diagonally (about 60°) fromits position in layer 310. Similarly, layer 320 depicts a printhead pathwith the same set of lines rotated counterclockwise diagonally (about−60°) from its position in layer 310.

The triangular-hole predicted cumulative deposit 340 is formed bystacking successive groupings of these three different layers 310, 320,330 one grouping after the other grouping. These layers are positionedrelative to each other with respect to the horizontal plane of depositso that the overlapping portions of the 3D-printed layers intercept atabout their center. In accordance with embodiments, the groupings canfollow a non-repeating permutation sequence; or a random sequence.

The trajectory path for each of the multiple layers is determined by anembodying algorithm (described below). The algorithm receives designspecification parameters for a medical-modality collimator. The designspecifications can be in the form of a CAD file describing the design ofthe collimator to be printed on the 3D printer. In otherimplementations, the design specifications can be stored as one or moredatabase records (e.g., objects, tabular data, etc.), or other formats.

FIG. 3B depicts synthesized results 360, 370, 380 for individual layers310, 320, 330 and a synthesized cumulative result 390 for the multiplelayers depicted in FIG. 3A in accordance with embodiments.

The conventional, synthesized cumulative result illustrated in FIG. 2C(produced by multiple cycles retracing along the same printhead path)does not result in a collimator having straight septa of equal length toform the hexagonal channels depicted in FIG. 2B. However, synthesizedcumulative result 380 produced in accordance with embodiments results instraight septa of about equal length to form the perimeter of a trianglewith about equal sides, resulting in collimator having about triangularmatrix of channels.

In accordance with embodiments, a physical collimator represented bysynthesized cumulative result 390 can be produced by stacking groupingsof printer path layer 310, printer path layer 320, and printer pathlayer 330 to create triangular patterns. The deposition of the extrudedmaterial within the collimator's field-of-view is along straight lines,with all turns made outside the field-of-view. Multiple renditions ofthe stacked grouped layers are deposited to build the septa walls to thedesired height. In accordance with implementations, collimators withhexagonal, square, triangular, or other perimeter channels can beproduced.

In accordance with embodiments, the ordering of the multiple pathswithin each stacked grouping can be varied between groups. In someimplementations, the ordering within a stack grouping can be sequential(e.g., ABC, ABC, ABC, . . . ), stepped (e.g., ABC, BCA, CAB, . . . ),random (ABC, BAC, CBA, . . . ), or a non-repeating permutation—where“A”, “B” and “C” represent different types of 3D printhead trajectorypath patterns (e.g., layers 310, 320, 330). The variation in stackgrouping can reduce manufacturing imaging artifacts in the 3D printedcollimator, thus improving its overall performance. The thickness oflayers, and/or successive layers can also reduce manufacturing imagingartifacts and, thus, improve the collimator performance.

For a given design specification of a medical-modality collimator, thefollowing parameters can be determined:

-   -   p!: the number of permutations of p types of layers without        repetition;    -   n: the number of 3D printed layers;    -   p: the number of types of layers;    -   d: the thickness of a 3D-printed layer; and    -   t: the overall collimator thickness.

For example, for a triangular-hole collimator, p=3 (layers) and p!=6(quantity of layer permutation types). In accordance with oneimplementation, the sequence of permutations can be:

-   -   Layer grouping permutation #1: [A,B,C];    -   Layer grouping permutation #2: [B,A,C];    -   Layer grouping permutation #3: [C,A,B];    -   Layer grouping permutation #4: [A,C,B];    -   Layer grouping permutation #5: [B,C,A];    -   Layer grouping permutation #6: [C,A,B].

Based on the collimator design specifications, embodying systems andmethods can determine the number of layer permutations, and the groupingpattern for within each layer. For example, a non-repeating permutationsequence can be determined as follows:

The quantity of non-repeating permutation sequences (l) can bepre-generated for storage in memory:

k ₀ =p! ⁰×(p×p!)

k ₁ =p! ¹×(p×p!)

k ₂ =p! ²×(p×p!)

* * *

k _(l) =p! ^(l)×(p×p!)

Where k_(l) represents the quantity of elements of the l^(th)permutation sequence. For instance, for p=3,

k₀=18:

-   -   [A,B,C,B,A,C,C,A,B,A,C,B,B,C,A,C,A,B]

k₁=108:

-   -   [A,B,C,B,A,C,C,A,B,A,C,B,B,C,A,C,A,B,C,A,B,A,C,B,A,B,C,B,A,C,B,        C,A,C,A,B,B,C,A,C,A,B,A,B,C,B,A,C,C,A,B,A,C,B,A,B,C,B,A,C,B,C,        A,C,A,B,C,A,B,A,C,B,C,A,B,A,C,B,B,C,A,C,A,B,A,B,C,B,A,C,B,C,A,        C,A,B,A,B,C,B,A,C,C,A,B,A,C,B]

and, k₂=648:

-   -   [A,B,C,B,A,C,C,A,B,A,C,B,B,C,A,C,A,B,C,A,B,A,C,B,A,B,C,B,A,C,B,        C,A,C,A,B,B,C,A,C,A,B,A,B,C,B,A,C,C,A,B,A,C,B,A,B,C,B,A,C,B,C,        A,C,A,B,C,A,B,A,C,B,C,A,B,A,C,B,B,C,A,C,A,B,A,B,C,B,A,C,B,C,A,        C,A,B,A,B,C,B,A,C,C,A,B,A,C,B,B,C,A,C,A,B,A,B,C,B,A,C,C,A,B,A,        C,B,A,B,C,B,A,C,B,C,A,C,A,B,C,A,B,A,C,B,A,B,C,B,A,C,C,A,B,A,C,        B,B,C,A,C,A,B,C,A,B,A,C,B,A,B,C,B,A,C,B,C,A,C,A,B,C,A,B,A,C,B,        B,C,A,C,A,B,A,B,C,B,A,C,B,C,A,C,A,B,A,B,C,B,A,C,C,A,B,A,C,B,C,        A,B,A,C,B,B,C,A,C,A,B,A,B,C,B,A,C,B,C,A,C,A,B,A,B,C,B,A,C,C,A,        B,A,C,B,A,B,C,B,A,C,C,A,B,A,C,B,B,C,A,C,A,B,C,A,B,A,C,B,A,B,C,        B,A,C,B,C,A,C,A,B,B,C,A,C,A,B,A,B,C,B,A,C,C,A,B,A,C,B,A,B,C,B,        A,C,B,C,A,C,A,B,C,A,B,A,C,B,A,B,C,B,A,C,C,A,B,A,C,B,B,C,A,C,A,        B,C,A,B,A,C,B,A,B,C,B,A,C,B,C,A,C,A,B,C,A,B,A,C,B,B,C,A,C,A,B,        A,B,C,B,A,C,B,C,A,C,A,B,A,B,C,B,A,C,C,A,B,A,C,B,B,C,A,C,A,B,A,        B,C,B,A,C,C,A,B,A,C,B,A,B,C,B,A,C,B,C,A,C,A,B,C,A,B,A,C,B,B,C,        A,C,A,B,A,B,C,B,A,C,C,A,B,A,C,B,A,B,C,B,A,C,B,C,A,C,A,B,C,A,B,        A,C,B,C,A,B,A,C,B,B,C,A,C,A,B,A,B,C,B,A,C,B,C,A,C,A,B,A,B,C,B,        A,C,C,A,B,A,C,B,A,B,C,B,A,C,C,A,B,A,C,B,B,C,A,C,A,B,C,A,B,A,C,        B,A,B,C,B,A,C,B,C,A,C,A,B,C,A,B,A,C,B,B,C,A,C,A,B,A,B,C,B,A,C,        B,C,A,C,A,B,A,B,C,B,A,C,C,A,B,A,C,B,A,B,C,B,A,C,C,A,B,A,C,B,B,        C,A,C,A,B,C,A,B,A,C,B,A,B,C,B,A,C,B,C,A,C,A,B,B,C,A,C,A,B,A,B,        C,B,A,C,C,A,B,A,C,B,A,B,C,B,A,C,B,C,A,C,A,B,C,A,B,A,C,B]

These sequences are generated using permutations of previouslypermutated sequences. The following is an embodying step-by-stepdescription:

1) Beginning with different types of layers A, B, C (e.g., layer 310,layer 320, layer 330), define an initial set of sequences A′, B′ and C′(e.g., A′=A, B′=B, and C′=C): A′=[A], B′=[B], C′=[C];

2) Generate a non-repeating sequence of “ABC's” based on previous valuesof “A′B′C's”, obtained from Step 1, where the base permutation sequence(A′B′C′) does not change: [A′,B′,C′]; [B′,A′,C′]; [C′,A′,B′];[A′,C′,B′]; [B′,C′,A′]; [C′,A′,B′];

3) Define new values for A′, B′ and C′, based on the previous step, bysubdividing the previous sequence into three consecutive regions:A′=[A,B,C,B,A,C], B′=[C,A,B,A,C,B], C′=[B,C,A,C,A,B] (see k₀=18 above);

4) Generate a non-repeating sequence of “ABC's” based on values of“A′B′C's” obtained from previous step, where the base permutationsequence “A′B′C's” does not change: [A′,B′,C′]; [B′,A′,C′]; [C′,A′,B′];[A′,C′,B′]; [B′,C′,A′]; [C′,A′,B′] (see k₁=108 above);

5) Define A′, B′ and C′ with new values, based on previous step, bysubdividing the previous sequence in three consecutive regions:

-   -   A′=[A,B,C,B,A,C, C,A,B,A,C,B, B,C,A,C,A,B,C,A,B,A,C,B,        A,B,C,B,A,C, B,C,A,C,A,B]    -   B′=[B,C,A,C,A,B, A,B,C,B,A,C, C,A,B,A,C,B,A,B,C,B,A,C,        B,C,A,C,A,B, C,A,B,A,C,B]    -   C′=[C,A,B,A,C,B, B,C,A,C,A,B, A,B,C,B,A,C,B,C,A,C,A,B,        A,B,C,B,A,C, C,A,B,A,C,B]

6) Generate a non-repeating sequence of ABC based on values of A′B′C′obtained from the previous step, where the base permutation sequenceA′B′C′ does not change: [A′,B′,C′]; [B′,A′,C′]; [C′,A′,B′]; [A′,C′,B′];[B′,C′,A′]; [C′,A′,B′] (see k₂=648 above)

7) Repeat above steps until a sequence is generated to satisfy thedesign specifications for the collimator based on layer thickness d, andthe overall collimator thickness t, (i.e., k>t/d).

Knowing the pre-generated permutation sequences (steps 1-7), a 3D printsequence for the STL file can be assembled based on a ratio of theoverall collimator thickness to the layer thickness (t/d), and thenumber of members of each permutation (kg):

-   -   If m=(t/d)≤k₀, grab a quantity of m sequence elements from k₀.        For instance, if m=12, the sequence of layers can be the first        twelve elements of sequence k₀—[A,B,C,B,A,C,C,A,B,A,C,B].    -   If k₁≥m=(t/d)>k₀, grab a quantity of m sequence elements from        k₁. For instance, if m=30, the sequence of layers consists of        the first 30 elements of sequence        k₁—[A,B,C,B,A,C,C,A,B,A,C,B,B,C,A,C,A,B,C,A,B,A,C,B,A,B,C,B,A,C].    -   If k₂≥m=(t/d)>k₁, grab a quantity of m sequence elements from        k₂. For instance, if m=640, the sequence of layers consists of        the first 640 elements of sequence k₂.

FIG. 4 is a flowchart for process 400 to create a STL file formanufacturing a printed collimator in accordance with embodiments. TheSTL file includes instructions to control a 3D printer to producegroupings of layered printhead paths in accordance with embodiments.

The design specification parameters for a medical-modality collimatorare received, step 410. The parameters can be obtained from a CAD file,database record(s), or other memory and/or file. Parameters can includethe collimator channel pattern (e.g., square, triangular, hexagonal,etc.), the septum wall width, overall collimator thickness.

Determine the number of deposit layer permutation sequence, step 420.The number of layers is related to the number of walls to form thechannel (e.g., triangular channel has 3 permutation sequences. Calculatethe number of permutation layer elements (1Q) to be deposited for eachlayer, step 430. The number of permutation layers is related to thedeposit layer thickness and the overall collimator design specificationthickness. For each permutation layer, step 440, generate a quantity ofsequences formed from a base permutation sequence. The quantity ofsequences is dependent on the layer thickness.

Once the sequences for each permutation layer is generated, thesepermutation layers can be assembled, step 450, to form a 3D printerfile, e.g., a STL format file and/or object. The assembled 3D print filecan be provided, step 460, to a 3D printer. By following the permutationsequences and layers specified in the 3D print file, a 3D printer canmanufacture, step 470, a medical collimator based on the assembled setsof permutation layers.

FIG. 5 depicts 3D printer system 500 for producing a medical-modalitycollimator in accordance with embodiments. System 500 includes 3Dprinter 510 in communication across an electronic network (not shown)with control processor 520. Control processor 520 can access executableinstructions 532 in data store 530, which causes the control processorto control components of system 500. Dedicated hardware, softwaremodules, and/or firmware can implement embodying services disclosedherein.

Layered-sequence algorithm 534 can be executed by the control processorto perform the steps outlined above to create 3D print file 538, whichspecifies to 3D printer 510 a sequencing of additive layers havingpermutations within each layer to create the medical modalitycollimator. The specifications for the medical-modality collimator canbe stored in collimator design specification 536, or provide to thecontrol processor across the electronic communication network.Pre-generated permutation sequences 539 may also be stored and accessedby the processor for generating sets of sequences.

In accordance with some embodiments, a computer program applicationstored in non-volatile memory or computer-readable medium (e.g.,register memory, processor cache, RAM, ROM, hard drive, flash memory, CDROM, magnetic media, etc.) may include code or executable instructionsthat when executed may instruct and/or cause a controller or processorto perform methods disclosed herein, such as a method to produce astereolithography file to instruct a 3D printer to manufacture a 3Dprinted collimator, as described above.

The computer-readable medium may be a non-transitory computer-readablemedia including all forms and types of memory and all computer-readablemedia except for a transitory, propagating signal. In oneimplementation, the non-volatile memory or computer-readable medium maybe external memory.

Although specific hardware and methods have been described herein, notethat any number of other configurations may be provided in accordancewith embodiments of the invention. Thus, while there have been shown,described, and pointed out fundamental novel features of the invention,it will be understood that various omissions, substitutions, and changesin the form and details of the illustrated embodiments, and in theiroperation, may be made by those skilled in the art without departingfrom the spirit and scope of the invention. Substitutions of elementsfrom one embodiment to another are also fully intended and contemplated.The invention is defined solely with regard to the claims appendedhereto, and equivalents of the recitations therein.

I claim:
 1. A method of manufacturing a collimator (134) on athree-dimensional printer (510), the method comprising: obtaining designspecifications (536) for the collimator, the design specificationsincluding a channel perimeter pattern and an overall collimatorthickness; determining a first quantity of deposit layer permutationtypes based on the channel perimeter pattern; determining a respectivesecond quantity of permutation layer elements (310, 320, 330) for eachrespective one of the deposit layer permutations; generating respectivesets of sequences for each respective one of the deposit layerpermutations, the number of sets equal to the respective second quantityfor the corresponding deposit layer permutations; assembling therespective sets of sequences into a three-dimensional print file (538),providing the three-dimensional file to the three-dimensional printer;and manufacturing the collimator by depositing additive layers ofmaterial based on contents of the three-dimensional file.
 2. The methodof claim 1, including obtaining the design specifications by one ofaccessing a data store record and receiving a file.
 3. The method ofclaim 1, including determining the first quantity as a factorialfunction of the channel perimeter pattern.
 4. The method of claim 1,each respective sets of sequences including a series of patterns ofindividual additive layers to be printed by the three-dimensionalprinter.
 5. The method of claim 1, including: pre-generating permutationsequences based on one or more channel perimeter patternsconfigurations; storing the pre-generated permutation sequences in adata record; and the generating sets of sequences including accessingthe pre-generated permutation sequences (539).
 6. The method of claim 1,the generating sets of sequences including: defining an initial basepermutation sequence based on the first quantity; generating a firstsequence of permutations, each permutation containing a plurality ofnon-repeating elements, where the non-repeating element includesmultiples of the base permutation sequence; subdividing the firstsequence into a quantity of consecutive regions equal to the firstquantity; generating second and more sequences of permutations;appending each of the second and more sequences to the first sequence;if the first sequence does not include a quantity of permutations thatsatisfies collimator design requirements based on additive layerthickness of the three-dimensional printer and an overall collimatorthickness, then repeat the generation and subdividing steps.
 7. Anon-transitory computer-readable medium having stored thereoninstructions which when executed by a processor cause the processor toperform a method of manufacturing a collimator (134) on athree-dimensional printer (510), the method comprising: obtaining designspecifications (536) for the collimator, the design specificationsincluding a channel perimeter pattern and an overall collimatorthickness; determining a first quantity of deposit layer permutationtypes based on the channel perimeter pattern; determining a respectivesecond quantity of permutation layer elements (310, 320, 330) for eachrespective one of the deposit layer permutations; generating respectivesets of sequences for each respective one of the deposit layerpermutations, the number of sets equal to the respective second quantityfor the corresponding deposit layer permutations; assembling therespective sets of sequences into a three-dimensional print file (538),providing the three-dimensional file to the three-dimensional printer;and manufacturing the collimator by depositing additive layers ofmaterial based on contents of the three-dimensional file.
 8. The mediumof claim 7, including instructions to cause the processor to perform thestep of obtaining the design specifications by one of accessing a datastore record and receiving a file.
 9. The medium of claim 7, includinginstructions to cause the processor to perform the step of determiningthe first quantity as a factorial function of the channel perimeterpattern.
 10. The medium of claim 7, including instructions to cause theprocessor to perform the step of including in each respective sets ofsequences a series of patterns of individual additive layers to beprinted by the three-dimensional printer.
 11. The medium of claim 7,including instructions to cause the processor to perform the steps of:pre-generating permutation sequences based on one or more channelperimeter patterns configurations; storing the pre-generated permutationsequences in a data record; and the generating sets of sequencesincluding accessing the pre-generated permutation sequences (539). 12.The medium of claim 7, including instructions to cause the processor toperform the step of generating sets of sequences by including: definingan initial base permutation sequence based on the first quantity;generating a first sequence of permutations, each permutation containinga plurality of non-repeating elements, where the non-repeating elementincludes multiples of the base permutation sequence; subdividing thefirst sequence into a quantity of consecutive regions equal to the firstquantity; generating second and more sequences of permutations;appending each of the second and more sequences to the first sequence;and if the first sequence does not include a quantity of permutationsthat satisfies collimator design requirements based on additive layerthickness of the three-dimensional printer and an overall collimatorthickness, the repeat the generation and subdividing steps.
 13. A systemfor manufacturing a collimator (134) on a three-dimensional printer(510), the system comprising: the three-dimensional printer incommunication with a control processor (520); the control processor incommunication with a data store (530), the data store includingexecutable instructions (532) that cause the control processor toperform a method, the method including: obtaining design specifications(536) for the collimator, the design specifications including a channelperimeter pattern and an overall collimator thickness; determining afirst quantity of deposit layer permutation types based on the channelperimeter pattern; determining a respective second quantity ofpermutation layer elements (310, 320, 330) for each respective one ofthe deposit layer permutations; generating respective sets of sequencesfor each respective one of the deposit layer permutations, the number ofsets equal to the respective second quantity for the correspondingdeposit layer permutations; assembling the respective sets of sequencesinto a three-dimensional print file (538), providing thethree-dimensional file to the three-dimensional printer; andmanufacturing the collimator by depositing additive layers of materialbased on contents of the three-dimensional file.
 14. The system of claim13, the executable instructions causing the control processor to performthe method by including: pre-generating permutation sequences based onone or more channel perimeter patterns configurations; storing thepre-generated permutation sequences in a data record; and the generatingsets of sequences including accessing the pre-generated permutationsequences (539).
 15. The system of claim 13, the executable instructionscausing the control processor to perform the method by including in thestep of generating sets of sequences: defining an initial basepermutation sequence based on the first quantity; generating a firstsequence of permutations, each permutation containing a plurality ofnon-repeating elements, where the non-repeating element includesmultiples of the base permutation sequence; subdividing the firstsequence into a quantity of consecutive regions equal to the firstquantity; generating second and more sequences of permutations;appending each of the second and more sequences to the first sequence;and if the first sequence does not include a quantity of permutationsthat satisfies collimator design requirements based on additive layerthickness of the three-dimensional printer and an overall collimatorthickness, then repeat the generation and subdividing steps.